Zeolites are aluminosilicate crystalline materials having rather uniform pore sizes which, depending upon the type of zeolite and the type and amount of cations included in the zeolite lattice, typically range from about 3 to 10 Angstroms in diameter. Both synthetic and natural zeolites and their use in promoting certain reactions, including the selective reduction of nitrogen oxides with ammonia in the presence of oxygen, are well known in the art.
One particular zeolite that has found use as a catalyst is chabazite (CHA). Methods for its preparation are known in the art. For example, U.S. Pat. No. 4,544,538 to Zones discloses the synthetic preparation of high silica form (Si/Al ratio of ˜15-30) of chabazite known as SSZ-13. It is prepared using an organically templated (N,N,N-trimethyl-1-adamantammonium) hydrothermal synthesis at high temperature (˜150° C.) and autogenous pressure.
There is a desire to obtain and/or prepare CHA catalysts via processes other than the organically templated hydrothermal synthesis process used to prepare the high silica SSZ-13 CHA. In this way, it is possible that CHA catalysts can be obtained and/or prepared in a more affordable and economical manner. In addition, CHA catalysts obtained from sources that do not utilize organically template hydrothermal synthesis.